Changeset 33297 in project

Timestamp:

04/18/16 01:16:12 (5 years ago)

Author:

John Foerch

Message:

Wrapping simple structs: how to do it with foreigners

File:

• wiki/Wrapping simple c structs (modified) (1 diff)

wiki/Wrapping simple c structs

@@ -34 +34 @@
 
 </enscript>
+
+
+; Using Foreigners
+
+Here is another way to wrap the same struct, this time using define-foreign-record-type from foreigners.
+
+<enscript highlight="scheme">
+(use foreigners)
+
+(foreign-declare "#include <SDL/SDL.h>")
+
+(define-foreign-record-type (sdl-rect SDL_Rect)
+  (short x sdl-rect-x sdl-rect-x-set!)
+  (short y sdl-rect-y sdl-rect-y-set!)
+  (unsigned-short w sdl-rect-w sdl-rect-w-set!)
+  (unsigned-short h sdl-rect-h sdl-rect-h-set!))
+
+(define make-sdl-rect
+  (foreign-lambda* sdl-rect
+      ((short x) (short y) (unsigned-short w) (unsigned-short h))
+    "SDL_Rect* r = (SDL_Rect*)malloc(sizeof(SDL_Rect));"
+    "r->x = x;"
+    "r->y = y;"
+    "r->w = w;"
+    "r->h = h;"
+    "C_return(r);"))
+
+(define a (make-sdl-rect 10 20 30 40))
+
+(print a ": " (sdl-rect-x a) " " (sdl-rect-y a) " "
+       (sdl-rect-w a) " " (sdl-rect-h a) " ")
+
+(sdl-rect-x-set! a 5)
+(sdl-rect-y-set! a 10)
+(sdl-rect-w-set! a 15)
+(sdl-rect-h-set! a 20)
+
+(print a ": " (sdl-rect-x a) " " (sdl-rect-y a) " "
+       (sdl-rect-w a) " " (sdl-rect-h a) " ")
+</enscript>